Cinetozona
Cinetozona Olomo et al., 1998 (ref. ID; 7452 original paper)
[ref. ID; 7452]
Diagnosis; Very small (20-35 um) ciliates; paroral dikinetid C-shaped; somatic kineties bipolar-the majority of which are reduced, and develop a ciliary girdle near the equator of the cell; oral area sub-equatorial, posteriad of the level of the ciliary girdle; somatic kinety n (the last somatic kinety) very short, and located on the left of the oral region; oral polykinetids composed of three transverse files, each having three rows of basal bodies, all at the anterior end of a shallow buccal cavity and encircled by the oral dikinetid. (ref. ID; 7452)
Etymology; From the Greek "kinein" to move, and "zone" girdle. (ref. ID; 7452)
Type species; Cinetozona pyriformis (ref. ID; 7452)
- Cinetozona pyriformis Olomo et al., 1998 (ref. ID; 7452 original paper)
Cinetozona pyriformis Olomo et al., 1998 (ref. ID; 7452 original paper)
Diagnosis
Very small, 20-35 um, pear-shaped ciliate with the characteristic cell outline of an inverted water drop. Most of the somatic infraciliature is reduced to a belt of kineties placed anteriad to the equator of the cell; one caudal cilium. With characteristics of the genus. (ref. ID; 7452)
Descriptions
The living ciliates have a costant and peculiar shape, retained even after fixation of silver impregnation. The body is pear-shaped, with a widened anterior half tapering towards a narrower posterior end. The posterior part of the cell is tail-like, swings when the ciliate moves, and bears a single caudal cilium. An indentation in the body outline, posteriad of the cell equator, marks the opening of the buccal aperture. The ciliates swim by continually rotating around the principal axis of the cell, in a manner reminiscent of a swimming Urozona Schewiakoff, 1889. There are small size and movement make them easily confused with flagellates of the genus Chilomonas Ehrenberg, 1859. The contractile vacuole is at the posterior pole of the cell, and its pore opens on the dorsal surface of the ciliate, at the end of somatic kinety 7. In most of the specimens examined the macronucleus was either spherical or ellipsoidal, and the number varied between one and four, typically one. The micronucleus is spherical, and lies close to the macronucleus. (ref. ID; 7452)
- Somatic infraciliature: Twenty-one to twenty-three bipolar somatic kineties form the somatic infraciliature. All except two are shortened and, with the exception of kinety n, develop a ciliary belt placed just anteriad to the equator of the cell, above an imaginary line separating the anterior and posterior halves of the cell. Each kinety bears eight dikinetids, except kinety 1 (with 14 dikinetids), and kinety 2 (with 11 dikinetids). The anterior part of kinety 1 originates beneath the level of the remaining somatic kineties, curving and following the oral dikinetids, to reach the posterior end of the cell. The posterior half of somatic kinety 2 consists of three pairs of basal bodies. The kinetodesmal fibre is long, except in the posterior portion of kinety 2. At the end of each of the last three or four somatic kineties, and opposite the posterior end of the oral dikinetid, there is one isolated kinetosome well separated from the nearest dikinetid within the same kinety. These isolated basal bodies do not form part of the ciliary girdle. Somatic kinety n (SK-n, the last somatic kinety) is very short, and is located on the left of the oral structures. This kinety consists of one row of 6-8 kinetosomes, as in Cinetochilum Perty, 1852, that appeared scattered in some silver-impregnated specimens. Close to the end of the posterior part of the cell there is one pair of kinetosomes that bears one caudal cilium. (ref. ID; 7452)
- Oral infraciliature: The oral aperture opens beneath the equator of the cell, and the complete set of oral structures is placed beneath the girdle of somatic kineties. The oral dikinetid is C-shaped, with the evident zigzag arrangement of kinetosomes typical of the genus Cinetochilum. There are three oral polykinetids (PK1, PK2, and PK3) organized as three transverse files, each with three rows of kinetosomes. PK2 is the longest polykinetids, and PK3 is the shortest. All three oral polykinetids are located in the upper half of the oral area, and are enclosed by the oral dikinetid. The scuticovestige is arranged in two parts: 1) five pairs of kinetosomes are arranged in a row, and placed diagonally underneath the posterior portion of the oral dikinetid, on its right side; 2) two to three pairs of kinetosomes transverse to the posterior end of the oral dikinetid. (ref. ID; 7452)
Comparison with similar genera
Establishing lineage relationships between ciliate species is always debatable, and it bonds with the systematist's preferences (e.g. nuclear structure and dualism; morphogenesis and stomatogenesis; morphological conservatism). To help elucidate phylogenetic affinities, Lynn (1979, 1981, 1996) proposed the structural consercatism hypothesis: "somatic structures are usually more reliable indicators of common ancestry than oral structures because of stronger selection acting on the latter". The evolutionary explanations to support such as hypothesis go beyond the scope of this paper. However, here we have found a ciliate, Cinetozona pyriformis n. g., n. sp., which seems to bear characteristics of several scuticociliate families, and perhaps Lynn's hypothesis may throw some insights. Uropedalium Kahl, 1928, Urozona, and Cinetochilum are the three genera which, in different ways, offer species that resemble C. pyriformis-all three belong to different families. Although size, shape and movement of living organisms C. pyriformis match Kahl's description for Uropedalium pyriforme, the oral and somatic infraciliature of any Uropedalium species instantly segregates it from Cinetozona. The oral polykinetid 1 in Uropedalium is one file of basal bodies along the anterior left margin of the oral region, and is not encircled by the paroral dikinetid. Furthermore, the latter varies in length, and is never C-shaped. The arrangement of the somatic kineties differs entirely from that in Cinetozona too. As neither the oral nor the somatic infraciliature of these two genera share common characteristics, we do not include Cinetozona within the Uronematidae. Incidentally, Uronema parva and Uropedalium sp. in Thompson (1972) are identical, and are here combined under the nominal species U. opisthostomum (Lepsi, 1926) (Uropedalium parvum is a junior synonym). The family Urozonidae, with one genus Urozona and only one species U. buetschlii, is remarkably similar to Cinetozona, with which the living cells are easily mistaken. The oral pattern in Urozona incorporates a straight paroral dikinetid, slightly curved at its posterior end, and an oral polykinetid 1 never enclosed by the paroral kinety. Thus, oral infraciliature in Urozona does not help to establish a family relationship with Cinetozona. But, what about the somatic infraciliature? Both genera have shortened somatic kineties restricted to a ciliary girdle at the cell equator (Urozona) or just anteriad to it (Cinetozona). At first glimpse, both somatic infraciliatures seem quite closely related. However, the presence in Cinetozona of a very short kinety n (the last somatic kinety) to the left of the oral region gives the key feature for exclusion from the Urozonidae: the small and displaced kinety n is absent in Urozona. Hence, close examination of the somatic structures, supported by the absence of common characters in the oral infraciliatures, excludes Cinetozona from the family Urozonidae. The analogous belt of short somatic kineties is just a convergent feature with no further phylogenetic implications. Cinetochilum is the third genus resembling Cinetozona, and it too has only one species, C. margaritaceum. The oral patterns in the two genera are virtually identical: C-shaped paroral dikinetid, structure and arrangement of the oral polykinetids (enclosed by the paroral kinety), and the scuticovestige. Interestingly, the somatic infraciliatures in the two genera are apparently different. At this point, Lynn's hypothesis on the conservativeness of the somatic structures to establish lineage relationships does seem to fail. But again, the presence in both genera of a short somatic kinety n to the left of the oral structures is the key conservative character that resolves the dilemma. Additionally, morphogenesis and stomatogenesis are similar in both species (pers. obserb., Tellez, 1981, Dissertation). All these shared characteristics justify the inclusion of Cinetozona within the family Cinetochilidae. (ref. ID; 7452)
Etymology
From the Latin "pyriformis", pear-shaped. (ref. ID; 7452)
Type location
Artificial freshwater pond in the garden of the Escuela de Ingenieros Tecnicos Forestales in the Campus of Universidad Complutense de Madrid, Spain. (ref. ID; 7452)
Specimens deposited
A holotype specimen (silver-impregnated organisms in a permanent slide, registration number MNCN 39.02/2) has been deposited with the Museo Nacional de Ciencias Naturales de Madrid, Spain. (ref. ID; 7452)